U.S. patent application Ser. No. 08/140,928 filed Oct. 25, 1993 entitled "Induction Motor Protective Circuit Breaker Unit" describes the use of a fuse unit connected in series with an electric circuit breaker to protect an electric motor and associated equipment. When any of the fuses are subjected to short-circuit currents, the fuse must be timely replaced. Since a separate fuse is inserted within each phase of a multi-phase electrical distribution system, the blown fuse within an associated phase must be replaced before the circuit breaker is turned on. This is to prevent so-called "single phasing" whereby the current transfers through the remaining phases causing damage to the wiring and associated electrical equipment.
U.S. Pat. Nos. 3,893,052, 4,068,283, and 4,274,121 each describe the use of circuit breakers with "targets" that are associated with the separate phases within a protected circuit to provide visual indication to an operator as to which of the phases has experienced overcurrent circuit interruption.
When such circuit breakers are used within electrical equipment enclosures, and the circuit breakers are turned off and on by remote handle operating devices, the operator may not know that one of the fuses is blown, or that a short circuit condition has occurred.
One purpose of the invention, is to prevent the circuit breaker from being turned on after a fault occurrence until the operator has determined the nature of the fault and that all the phases within the multi-phase system are operational after the fault is cleared.